Artificial food casings are used throughout the world in the processing of a great variety of meat and other food products including sausages of various types, products made from emulsified formulations, chunk and formed products and whole muscle products.
Various materials are used for forming artificial food casings including collagen and plastic films but a most common material is regenerated cellulose. One type of cellulose food casings, known in the art as "fibrous casing" is formed with a reinforcing fibrous material (such as paper) in the cellulose casing wall. Fibrous casing generally range in size from about 50 mm to 160 mm or more in diameter and have a wall thickness of about 0.07 mm to about 0.10 mm. Methods for forming fibrous casing using a regenerated cellulose are well known in the art and form no part of the present invention.
Fibrous casings are provided to the meat processor in one of several forms. One form called a "cut-length" is a relatively short piece of fibrous casing up to about 2.5 meters long. Each cut length, manually gathered onto a stuffing horn, provides sufficient casing for making only one, or at most, only a few stuffed products.
Fibrous casing also is sold in shirred form. Shirred casing is a relatively long casing length which has been gathered into closely nested pleats to considerably reduce the length of the casing article. For example, a shirred casing article may contain upwards of 70-80 meters of casing. Once a shirred casing article is placed on the horn of a stuffing machine, the machine can be run continuously for automatically producing a large number of stuffed products one after another.
Various shirring methods and apparatus are well known in the art including those disclosed in U.S. Pat. Nos. 2,983,949; 2,984,574; 3,454,982; and 3,988,804 among others.
For purposes of the present invention, it is sufficient to say that shirring involves inflating the casing and moving it onto a shirring mandrel where it is gathered into closely nested pleats formed against the mandrel. The shirred casing is longitudinally compacted to further reduce its length. The result, when the shirred casing is doffed from the mandrel, is a shirred casing article, sometimes referred to as a "shirred stick" having an internal bore to accommodate a stuffing horn.
Casing for shirring is supplied as feed stock in the form of a flat tube wound onto reels. Each reel contains upwards of 450-460 meters or more of casing. During shirring the flat tube is drawn from the reel and is inflated, shirred and then longitudinally compressed as described above to form individual sticks up to about 70-80 cm long with each stick containing 70-80 meters of casing. The length of the stick and the length of casing it contains depends in part on the diameter of the casing and diameter of the stuffing horn on which the casing is used.
Shirred sticks of fibrous casing do not retain their integrity because the tightly nested pleats tend to separate or deshirr so the coherency and integrity of the stick is broken. This renders the stick difficult to load onto a stuffing horn because the stick bore is no longer straight and uniform. Accordingly, techniques have been developed to maintain the integrity of a stick and facilitate handling. These techniques involve either the use of an internal or an external restraint.
An internal restraint generally is a tube which extends through the stick bore. In some cases pegs extending transversely through the tube at either end of the shirred stick holds the stick on the tube and maintains the integrity of the stick. In other cases the tube outside diameter and the bore diameter of the stick are selected and controlled so the casing pleats grip tightly about the tube with sufficient force to prevent an expansion and separation of the tightly nested pleats. External restraints include tubular netting which is drawn over the stick and then is gathered and closed over the ends of the stick. Other external restrains include tubular plastic film which is stretched over the stick. These plastic films contract or shrink down and press firmly against the outer surface of the stick and encompass at least a portion of the opposite ends of the stick to hold the stick together.
Fibrous casing articles in plastic film overwraps generally contain sufficient moisture to permit stuffing the casing as-is. The plastic film overwrap not only serves to retain the integrity of the stick but also helps to retard the loss of moisture. This ready-to-stuff casing is to be distinguished from fibrous casing which requires soaking prior to stuffing. Fibrous casings requiring soaking generally are packaged in netting to permit free access of the soak water to the surface of the casing article.
One problem associated with shirred fibrous casing is that the supply reel of feed stock casing for shirring is likely to contain one or more splices. This is because it is difficult to form a single casing length 450-460 meters long so shorter lengths are spliced together in order to obtain the total casing to fill a supply reel.
These splices are objectionable because even though the splice is able to pass through the shirring apparatus and become incorporated into a shirred stick, the splice is not stuffable. The presence of a splice is tolerated where the casing article is a shirred stick retained on a tubular core. In this case, the splice itself is evident by the color of the splice tape and is accessible because the outer surface of the shirred stick is not enclosed.
Certain stuffing machines as disclosed for example in U.S. Pat. No. 4,017,941, include an automatic shut-off to terminate the stuffing operation when the casing runs out. When stuffing a cored casing article containing a splice, on such a machine, the operator puts the casing article onto a stuffing horn and attaches a lanyard to the splice or to the casing pleats adjacent the splice. As casing is drawn forward from the shirred stick during stuffing, the lanyard eventually will pull taught and trigger operation of an end-of-casing sensor on the stuffing machine. This initiates a sequence of events for terminating the stuffing operation before the splice is stuffed. The operator now can clear the splice through the stuffing machine. After the splice is cleared through the stuffing machine the lanyard is reattached to the last pleats in the shirred stick and the stuffing operation restarted.
With other machines which do not have an automatic shut-off feature, the operator simply monitors the stuffing operation and manually turns the machine off just before the splice is stuffed. Thus, where a splice is present in a cored shirred casing article, it does not interfere with the shirring operation and has only some limited effect on the stuffing operation.
However, where the integrity of a shirred casing article is retained by an overwrap, particularly a plastic film overwrap such as a stretch film, the problem of splices historically has been more acute. The accepted procedure has been for the casing manufacturer to break the shirred stick at the splice, remove the splice and package the pieces of shirred casing in separate overwraps. This adds steps to the shirring operation and is an inconvenience to the shirring machine operator.
Also this procedure results in the production of so called "short sticks" containing less casing than a full length stick which is made with a continuous, unspliced length of casing. Short sticks are undesirable for several reasons. For example, packing cartons are designed to contain casing articles of a specified length. Consequently when packaging a mixture of short and full length sticks in a carton, care must be taken to insure that the short sticks are paired so that their combined length is the same as a full stick. This adds time and steps to the process of filling a carton with casing articles.
Meat processors also object to short sticks because they shorten the time of continuous operation and increase the idle time of the machine by increasing the frequency of stopping the machine to load fresh sticks onto the stuffing horn. Thus, in connection with shirred fibrous casing articles having an overwrap to maintain integrity, splices interrupt the shirring operation, and the resulting short sticks not only complicate packaging requirements, but also interfere with the continuous operation of the stuffing machine. Consequently, elimination of the need to remove splices from overwrapped shirred fibrous casing articles will benefit both the casing manufacturer and the casing user.